|||||||||||||||| USOO5147621A United States Patent (19) 11) Patent Number: 5,147,621 Schumann (45) Date of Patent: Sep. 15, 1992

54 METHOD FOR STABILIZING Assistant Examiner-Valerie Lund PHOSPHORUSTRICHLORIDE Attorney, Agent, or Firm-Jordan and Hamburg 75 Inventor: Rudolf Schumann, Raguhn, Fed. 57 ABSTRACT Rep. of Germany The invention relates to a method for stabilizing phos 73) Assignee: Chemie AG Bitterfeld-Wolfen, phorus trichloride. In order to delay the formation of Bitterfeld, Fed. Rep. of Germany phosphorus oxychloride in phosphorus trichloride and (21) Appl. No.: 665,512 to reduce it to a minimum value which no longer ad versely affects further processing, one or more amines 22 Filed: Mar. 6, 1991 which have at least two aromatic hydrocarbon groups 51) Int. C...... C01B 11/02 linked to one nitrogen atom, such as diphenylamine, 52 U.S. C...... 423/265; 423/300 phenothiazine, phenyl-4-methylphenylamine and tri 58) Field of Search ...... 423/300, 301, 265; phenylamine, are added to the phosphorus trichloride. 252/182.32, 399 The amines can also be added in the form of their salts, 56) References Cited including their quaternary ammonium compounds, or their reaction products with phosphorus halides. The U.S. PATENT DOCUMENTS amounts of amines, added fall within the range of 3,903,002 9/1975 Hotten ...... 252/46.7

10.6% to 10%, based on the amount of phosphorus 4,197,209 4/1980 Zinke et al...... 252/46.6 trichloride. 4,846,985 7/1989 Rizvi et al...... 252/48.2 Primary Examiner-Michael Lewis 20 Claims, No Drawings 5,147,621 2 rus trichloride and to reduce the quality losses of the METHOD FOR STABILIZING PHOSPHORUS phosphorus trichloride during storage and transport. TRICHLORIDE The task of the invention consists of providing a method for the stabilization of phosphorus trichloride, BACKGROUND OF THE INVENTION 5 during which the formation of phosphorus oxychloride The present invention relates to a method for stabiliz in the phosphorus trichloride is delayed significantly ing phosphorus trichloride. and reduced to a minimum value, which no longer Phosphorous trichloride is prepared industrially by adversely affects further processing. the reaction of phosphorus with chlorine. It generally Pursuant to the invention, this objective is accom contains less than 0.05% phosphorus oxychloride if it is 10 plished owing to the fact that one or more amines, prepared from purified chlorine, or if it is rectified when which have at least two aromatic hydrocarbon groups chlorine is used which has not been purified. linked to one nitrogen atom, are added to the phospho However, phosphorus trichloride can easily be oxi rus trichloride. dized by oxygen or oxygen-containing gases to phos phorus oxychloride. A slow, steady increase in the 15 DESCRIPTION OF THE PREFERRED phosphorus oxychloride content can be observed dur EMBODIMENTS ing storage, transport and use of phosphorus trichloride. The following compounds, for example, are used as The phosphorus oxychloride lowers the quality of the amines: phosphorus trichloride and necessarily leads to undesir diphenylamine able by-products during chemical processing, so that 20 phenyl-4-methylphenylamine the desired end product is of lower quality and is ob bis-(4-methylphenyl)-amine tained in a lesser yield. For example, in further process 2,6-dichloro-diphenylamine ing to phosphorus pentachloride or phosphorus sulfo 2-chloro-2',4-dinitrodiphenylamine chloride, all the phosphorus oxychloride reaches the N-isopropyl-N'-phenyl-4-phenylenediamine end product. Because of the physical properties, subse 25 N,N'-diphenyl-4-phenylenediamine quent separation is much more difficult than separation from phosphorus trichloride. During further processing phenothiazine to phosphorous acid, phosphoric acid is formed from phenyl-2-naphthylamine the phosphorus oxychloride and phosphates are formed diphenyl-methylamine as by-products during the reaction with alcohols to 30 diphenyl-cyclohexylamine phosphites. During the synthesis of tri-(2-chloroethyl) triphenylamine phosphite by reaction with ethylene oxide, tri-(2- The amines can also be added in the form of their chloroethyl) phosphate is formed as an interfering by salts, including their quaternary ammonium compounds product. or their reaction products with phosphorus halides. During the synthesis, storage and transport of phos 35 Such compounds, are, for example: phorus trichloride, care must therefore be taken to ex diphenylamine hydrochloride clude air or other oxygen-containing gases as far as diphenylamine hydrobromide possible. The storage of phosphorus trichloride under a diphenylamine hydronitrate slight excess pressure of a dry, oxygen-deficient inert triphenylamine hydrochloride gas is known (Chem. Techn.33 (1981), vol. 4, page 191). dimethyl-diphenyl-ammonium iodide In practice, the synthesis and transport of phosphorus dimethyl-diphenyl-ammonium-methyl sulfate trichloride are also carried out while largely excluding diphenylamino-dibromophosphan oxygen, if necessary, under the protection of an inert diphenylamino-dichlorophosphan gas, such as nitrogen or carbon dioxide. Nevertheless, bis-(diphenylamino)-chlorophosphan during prolonged transport and storage, oxygen has a 45 The amines can be added in dissolved or dispersed form. pronounced effect and there is formation of phosphorus Chloroform or methylene chloride, for example, are oxychloride. For example, when shipping tank car lots, used as solvent. The amines are added in an amount of concentrations of mainly 0.2% to 0.8% phosphorus 10.6% to 10.1%, based on the amount of phosphorus oxychloride occur. trichloride. It is also possible to add the amines to only Because of the high cost of energy and equipment, 50 a portion of the phosphorus trichloride and to mix this subsequent or repeated purification by distillation can portion subsequently with the remaining amount of not be given consideration. phosphorus trichloride. Decreasing the amount of and stabilizing the phos The amount of stabilizer depends on the intended phorus oxychloride by adsorbents, such as silica gel effect, such as the degree and duration of the stabiliza Gallus-Olender, I. and Franc, B.; Z. anorgan. allg. 55 tion, as well on the amine selected. Chem. 451 (1979), pages 189-192 and PL Patent 85 068) The stabilizer can also be formed or converted in situ. are also very disadvantageous because of the large ex For example, amines can be formed in the phosphorus penditure for equipment, the costs of the adsorbent, the trichloride from aminochlorophosphans and amine hy product losses and the disposal of waste. For example, drochlorides. The amines, which have at least two aro to lower the POCl3 content from 0.78% to 0.07%, cal matic hydrocarbon groups linked to one nitrogen atom, culated as H3PO4, and to stabilize the phosphorus tri stabilize the phosphorus trichloride outstandingly chloride, a contact time of 21 days and 10% silica gel, against the effects of oxygen or oxygen-containing based on the amount of phosphorus trichloride, are gases. The formation of phosphorus oxychloride in the required. phosphorus trichloride is delayed to such an extent and 65 reduced quantitatively to such a degree, that the phos SUMMARY OF THE INVENTION phorus trichloride retains almost its original quality It is an object of the present invention to decrease the even after having been stored or transported for several technical and economic expense of stabilizing phospho weeks. Further chemical processing of the phosphorus 5,147,621 3 4. trichloride can therefore be carried out without prob TABLE 1-continued lems and does not lead to any losses in yield or reduc % by Weight of tions in quality of the end products that are to be pro Anount Phosphorus' duced. Additive (ng) l 2 3 The invention will be described below by means of Triphenylamine 0.2) 0.03 8 0.0 two examples. Key to Table *1 before the action of oxygen EXAMPLE 1. 2 after the action of oxygen without additive 3 after the action of oxygen with additive In each case, 50 ml of phosphorus trichloride, freshly O dissolved in chloroform; concentration: 10 mg/ml dissolved in chloroform; concentration: 0.1 ng/ml prepared under industrial conditions, was filled into 500 dissolved in methylene chloride; concentration: 10 ng/ml ml glass flasks under dry, oxygen-deficient argon, after 1 day treated with one or several amines which have at least two aromatic hydrocarbon groups linked to one nitro gen atom, and mixed well. The argon was subsequently 5 EXAMPLE 2 replaced by ambient room air and the sample was stored To a gas wash bottle, equipped with reflux condenser at room temperature. Immediately before the admission and a glass frit for dispersing gas, 100 mL of phosphorus of air and 30 days later, samples were taken and ana trichloride with a phosphorus oxychloride content of lyzed by infrared spectrophotometry for their phospho 0.03% were added, mixed with the amine and treated 20 uniformly for one hour with 10 L of oxygen. Subse rus oxychloride content. In each case, three parallel quently, the phosphorus oxychloride content was oxidation experiments were set up and the average val checked by infrared spectrophotometry. The results ues were determined. obtained are compared with a sample without additive For comparison, three samples were prepared in the in the following Table 2. manner described above from each batch of phosphorus 25 trichloride starting material without addition of an TABLE 2 amine and the formation of phosphorus oxychloride Amount % by Weight of was investigated. The results are given in the following Additive (ng) Phosphorus Oxychloride Table . Diphenylamine 5 0.88 30 Diphenylamine 50 0.18 TABLE N,N'-diphenyl-4- 55) 45 phenylenediamine % by Weight of N,N'-Diphenyl-4- 505) 0.78 Amount Phosphorus" phenylenediamine Additive (ng) 2 3 None 20.40 Diphenylamine 0.03 6 0.05 35 added as a dispersion in chloroform: concentration: 20 mg/mL Phenyl-4-methylphenylamine 0.03 .6 0.14 Bis-(4-methylphenyl)-amine 0.03 6 0.13 I claim: 2,6-Dichloro-diphenylamine 0.03 .6 0.05 1. A method for stabilizing phosphorus trichloride, 2-Chloro-2',4- 10 0.03 .2 0,1 dinitrodiphenylamine comprising adding to a composition consisting essen N-Isopropyl-N'-phenyl-4- 0.03 6 0.05 tially of phosphorus trichloride a stabilizing agent se phenylenediamine lected from the group consisting of amines having at Phenothiazine 0.03 6 0.04 least two hydrocarbons linked to one nitrogen atom, Phenyl-2-naphthylamine O 0.03 16 0.04 Salts of said amines, reaction products of said amines Phenyl-2-naphthylamine 0.03 1.6 0.16 with phosphorus halides, and mixtures thereof. Diphenyl-methylamine 0.02 1.6 0.04 45 Diphenyl-cyclohexylamine 0.03 1.6 0. 2. The method of claim 1, further comprising adding Triphenylamine 0.02 1.4 0.07 said stabilizing agent in dissolved form. Diphenylamine hydrochloride 0.02 .6 0.03 3. The method of claim 1, further comprising adding Diphenylamine hydrobromide 0.03 6 0.05 said stabilizing agent in dispersed form. Diphenylamine hydronitrate 0.02 1.5 0.04 4. The method of claim 1, wherein said stabilizing Triphenylamine hydrochloride 0.02 1.6 0.09 50 Dimethyl-diphenyl-ammonium 0.02 1.6 0.04 agent is added in an amount of 10-6% to 10-1% by iodide weight, based on the amount of phosphorus trichloride. Dimethyl-diphenyl-annonium 0.02 1.6 0.05 5. The method of claim 1, wherein said stabilizing methylsulfate agent is selected from the group consisting of diphenyl Diphenylamino- 0.03 1.6 0.0 55 amine, phenyl-4-methylphenylamine, bis-(4-methyl dibromophosphan phenyl)-amine, 2,6-dichlorodiphenylamine, 2-chloro Diphenylamino- 1 0.03 1.6 0.06 dichlorophosphan 2,4-dinitrodiphenylamine, N-isopropyl-N'-phenyl-4- Bis-(diphenylamino)- 0.03 .6 0.06 phenylenediamine, N,N'-diphenyl-4-phenylenediamine, chlorophosphan phenothiazine, phenyl-2-naphthylamine, diphenyl Diphenylamine with 0.5 0.02 1.5 0.04 methylamine, diphenyl-cyclohexylamine, triphenyl triphenylamine each amine and mixtures thereof. Phenothiazine with 0.5 0.02 1.5 0.04 dimethyl 6. The method of claim 1, wherein said stabilizing diphenyl-annonium agent is selected from the group consisting of diphenyl iodide each anine hydrochloride, diphenylamine hydrobromide, Diphenylamine 0.2) 0.02 1.4 0.05 65 diphenylamine hydronitrate, triphenylamine hydro Diphenylamine 0.022) 0.02 1.4 0.09 chloride, dimethyl-diphenyl-ammonium iodide, dimeth Diphenylamine 0.0022) 0.02 1.04) 0604) yl-diphenyl-ammonium-methyl sulfate, di Diphenylamine 0.23) 0.02 1.4 0.06 phenylaminodibromophosphan, diphenylamino 5,147,621 5 6 dichlorophosphan, bis-(diphenylamino)-chlorophos group consisting of amines having at least two hydro phan and mixtures thereof. carbons linked to one nitrogen atom, salts of said 7. A method for stabilizing phosphorus trichloride, amines, reaction products of said amines with phospho comprising adding to a first portion consisting essen rus halides, and mixtures thereof. tially of phosphorus trichloride a stabilizing agent se 14. The composition of claim 13, wherein said stabi lected from the group consisting of amines having at lizing agent is dissolved in a solvent. least two hydrocarbons linked to one nitrogen atom, 15. The composition of claim 14, wherein said solvent salts of said amines, reaction products of said amines is selected from the group consisting of chloroform and with phosphorus halides, and mixtures thereof, and methylene chloride. subsequently adding thereto a second portion of phos 10 16. The composition of claim 13, wherein said stabi phorus trichloride. lizing agent is dispersed in a solvent. 8. The method of claim 7, further comprising adding 17. The composition of claim 16, wherein said solvent said stabilizing agent in dissolved form. is selected from the group consisting of chloroform and 9. The method of claim 7, further comprising adding methylene chloride. said stabilizing agent in dispersed form. 5 10. The method of claim 7, wherein said stabilizing 18. The composition of claim 13, wherein said stabi agent is added in an amount of 10.6% to 10.1% by lizing agent is selected from the group consisting of weight, based on the amount of phosphorus trichloride. diphenylamine, phenyl-4-methylphenylamine, bis-(4- 11. The method of claim 7, wherein said stabilizing methylphenyl)-amine, 2,6-dichloro-diphenylamine, 2 agent is selected from the group consisting of diphenyl 20 chloro-2',4-dinitrodiphenylamine, N-isopropyl-N'-phe amine, phenyl-4-methylphenylamine, bis-(4-methyl nyl-4-phenylenediamine, N,N'-diphenyl-4- phenyl)-amine, 2,6-dichlorodiphenylamine, 2-chloro phenylenediamine, phenothiazine, phenyl-2-naphthyla 2',4-dinitrodiphenylamine, N-isopropyl-N'-phenyl-4- mine, diphenylmethylamine, diphenyl-cyclohexyla phenylenediamine, N,N'-diphenyl-4-phenylenediamine, mine, triphenylamine and mixtures thereof. phenothiazine, phenyl-2-naphthylamine, diphenyl 25 19. The composition of claim 13, wherein said stabi methylamine, diphenyl-cyclohexylamine, triphenyl lizing agent is selected from the group consisting of amine and mixtures thereof. diphenylamine hydrochloride, diphenylamine hydro 12. The method of claim 7, wherein said stabilizing bromide, diphenylamine hydronitrate, triphenylamine agent is selected from the group consisting of diphenyl hydrochloride, dimethyl-diphenylammonium iodide, amine hydrochloride, diphenylamine hydrobromide, 30 dimethyl-diphenyl-ammonium-methyl sulfate, di diphenylamine hydronitrate, triphenylamine hydro phenylamino-dibromophosphan, diphenylamino chloride, dimethyl-diphenyl-ammonium iodide, dimeth dichlorophosphan, bis-(diphenylamino)-chlorophos yl-diphenyl-ammonium-methyl sulfate, di phan and mixtures thereof. phenylaminodibromophosphan, diphenylamino 20. The composition of claim 13, wherein said stabi dichlorophosphan, bis-(diphenylamino)-chlorophos 35 lizing agent is present in an amount of 10-6% to 10-1% phan and mixtures thereof. by weight, based on the amount of phosphorus trichlo 13. A composition consisting essentially of phospho ride. rus trichloride and a stabilizing agent selected from the r st k k k

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